One common type of interengaging fastener includes two opposed fastener members, each of which has a base and a plurality of headed elements that project from the base. By compressively engaging the fastener members, the fastener may be used to detachably fasten two articles together. Such fasteners are advantageous because they may be engaged with a relatively low compressive force, while requiring a relatively high tensile force to disengage. A further advantage is that such fastener members are inexpensive to produce when compared to fasteners having different (such as male and female) fastener members.
A conventional fastener including a pair of interengaging fastener members of the type described above is illustrated in FIG. 6. This fastener includes a first fastener member 1 and a second fastener member 2, each being generally formed from polymeric material. The first and second fastener members 1 and 2 are provided with generally flat bases 3 and 4, respectively, and a plurality of headed elements 5 arranged on the bases 3 and 4 in a predetermined spaced relationship. Each of the headed elements 5 includes a stem 6 projecting generally orthogonally from the base, and head 7 formed at an end of the stem. The head is generally hemispherical, and has a larger diameter than the stem. The head 7 of each headed element 5 has a generally flat locking surface 8 adjacent to the stem 6 and extending radially outward from the periphery of the stem 6, and a bulgingly curved surface 9 with an apex, positioned opposite to the stem 6 relative to the locking surface 8.
The first fastener member 1 and the second fastener member 2 may be positioned so that the bases 3 and 4 are arranged substantially parallel to each other, while the headed elements 5 are mutually opposed, as shown in FIG. 6(a). In this position, when a predetermined compressive engagement force is applied to the respective bases 3 and 4, the head 7 of the headed element 5 of one fastener member comes into contact with and slides against, at the curved surface 9 thereof, the heads 7 of the adjacent headed elements 5 of the other fastener member. In so doing, the stems 6 of the headed elements 5 bend laterally, and thus bypass the opposed headed elements in the space between the adjacent headed elements 5. This is shown in FIG. 6(b). In this position, the headed elements 5 of one fastener member are engaged at the locking surfaces 8 of the heads 7 thereof with the locking surfaces 8 of the heads 7 of the headed elements 5 of the other fastener member. Thus, the first fastener member 1 and the second fastener member 2 are releasably attached to each other.
In the conventional fastener made from two like fastener members having headed elements, the headed element in the respective fastener member is generally formed so that a length of the stem is longer than a height of the head. Therefore, when the fastener members are mutually interengaged, the heads of the headed elements of one fastener member can be moved within the space between the adjacent stems of the other fastener member. Stated differently, when the locking surface of the heads of the engaged fastener members are in contact with each other, a gap corresponding to a difference between the length of the stem and the height of the head is formed between the apex of the curved surface of the head of the headed element of one fastener member and the surface of the base on the other fastener member. This gap is used to allow the headed element to tilt during the interengagement process to reduce the engagement force, and thus it is not desirable to eliminate the gap described above.
Due to this gap, however, when the heads of the headed elements are relatively displaced while interengaged, noise may be generated between the heads, or between the head and the opposed stem, due to frictional contact. Even if the gap were to be eliminated, the noise may be still generated particularly between the locking surface of the heads, due to lateral movement therebetween caused by vibration or the like. Hence, it would be desirable to provide a fastener that reduces the generation of such noises, particularly for applications in which minimal noise is desired.